The aim of this project is to define the molecular mechanisms and biological contexts for blood leukocyte migration to specific tissue sites that are inflamed or infected. We have focused on chemoattractant proteins that mediate this process and have identified members of a large family of chemoattractant receptors that are deployed on the leukocyte cell surface. We have also identified members of a diverse group of chemoattractant and chemoattractant receptor mimics made by viruses, including herpesviruses, poxviruses and HIV. We use genomics, molecular biology, cell biology and epidemiology as the principle methods for analyzing these molecules. A major goal is to identify specific disease associations of individual chemoattractant and chemoattractant receptors, in order to identify potential new therapeutic targets. A key strategy is to analyze phenotypes of gene knockout mice in disease models as well as associations of loss of function mutations in the corresponding human genes in human disease cohorts. In FY09 we reported discoveries in the following three diseases: 1. West Nile virus pathogenesis;2. atherosclerosis;and 3.) renal ischemia-reperfusion injury. 1.) We found that among healthy individuals donating blood, homozygous mutation CCR5D32 is a risk factor for symptoms associated with WNV infection but not for infection per se. This extends our previous work in this area that identified this genotype as a risk factor for symptomatic WNV infection in patients presenting with symptomatic illness to a health care professional. The new study was based on comprehensive WNV testing of 35 million blood donations by the American Red Cross from the start of the screening program through July, 2008. The recent work is important because it provides new insight into the mechanism by which CCR5 deficiency increases risk of symptomatic WNV disease. The WNV work is particularly challenging because this is an ongoing emerging epidemic in which it is difficult to obtain useful samples. The overall results are scientifically important because they identify the first genetic risk factor for WNV disease and the first beneficial role in humans for CCR5. The significance extends beyond WNV to HIV/AIDS since CCR5 is exploited by HIV to enter target cells and since CCR5 antagonists are now being used in patients with HIV/AIDS. The new data suggest that blocking CCR5 with a drug may increase the risk of symptomatic WNV disease should treated patients become infected with WNV. 2.) In FY09 we reported that functional polymorphism in the gene encoding human OAS1 is a risk factor for infection with West Nile virus. This result translates to human previous data associating mouse OAS1b, the homologue of human OAS1, with susceptibility to flavivirus infection. The work is scientifically important because it provides some of the first data supporting a role for the endogenous Type I interferon signaling system, which includes OAS1, in control of a viral infection in man. 3.) In FY09 we reported that atherogenic lipids can induce high-density lipoprotein uptake and cholesterol efflux in human macrophages by up-regulating transmembrane chemokine CXCL16 without engaging CXCL16-dependent cell adhesion. CXCL16 is an unusual chemokine in that it has three distinct functions: adhesion, chemotaxis and scavenging. The scientific significance of this work is that it provides an explanation for genetic evidence linking CXCL16 to protection from atherosclerosis in mouse and man. 4.) In FY09 we reported the chemokine receptor CCR1 regulates inflammatory cell infiltration after renal ischemia-reperfusion injury. We found that CCR1 deficient mice had markedly reduced levels of neutrophils and macrophages in the injured kidney, yet this did not affect function, which declined at the same rate as in injured kidney from wild type mice. The data suggest that CCR1 dependent cell infiltration may be more important for tissue repair than for injury.